Author Topic: Con Rod Clearance & One Broke (Read 1294 times)

jakec · « **on:** March 11, 2020, 09:37:58 AM »

I was taking my connecting rod bearing clearances.

manual says factory .0007 - .0019

results:

1. .0017
2. .0017
3. .0017
4. .002

Sounds good.

However one of the connecting rod bolts wasn't torquing out, kept trying at it.. it eventually broke. All the others torqued up fine.

Does anyone have an extra one of these? Part #13213333003

Should I be worried about the other 7 bolts?

PeWe · « **Reply #1 on:** March 11, 2020, 09:58:19 AM »

I should replace them all. If one snapped, not overtightened it can have been tightened too hard before, all the other included and nuts.

CB750?
F2 bolts usually recommended in CB750 K SOHC.
Available here pos 6 & 7
https://www.cmsnl.com/honda-cb750f2-supersport-germany_model14692/partslist/E15.html#results

scrambler · « **Reply #2 on:** March 11, 2020, 10:06:35 AM »

I agree. You better sleep if you replace those.

bryanj · « **Reply #3 on:** March 11, 2020, 10:36:29 AM »

What bike, 333 midle number is 350/400

jakec · « **Reply #4 on:** March 11, 2020, 10:53:58 AM »

It is a 400F.

I'm sure I can get them cheaper if I'm getting 8 and I go through a better retailer. Really expensive to buy just one on ebay though.

bryanj · « **Reply #5 on:** March 11, 2020, 04:47:27 PM »

Price for a Honda part wont change much and it needs to be a proper part

jakec · « **Reply #6 on:** March 11, 2020, 05:23:11 PM »

I have found that you can get things like this (genuine) for $3 from a wholesaler, and $12-15 for a single on ebay. It's just not worth the s&h if you only need 1.

jakec · « **Reply #7 on:** March 12, 2020, 12:18:48 PM »

Best price I have found so far is $11 at DSS. That's $88 if I use the old nuts. If all other bolts torqued to the standard just fine, should I really replace? I have not seen this mentioned as a typical item to replace for a rebuild.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #8 on:** March 12, 2020, 01:05:40 PM »

I will say that more get reused rather than replaced...….

BenelliSEI · « **Reply #9 on:** March 12, 2020, 01:10:22 PM »

+1 to PEWE. If they have been over torqued before, and stretched, your taking a risk. I’d replace all of them.......

low-side · « **Reply #10 on:** March 12, 2020, 04:02:27 PM »

You're boots on the ground, so only you can make the call. How did it break? Does it have some big gap with missing or very dark material (void or inclusion) where it sheared off or did it twist apart like it was over-torqued? If it's the latter, I'd replace them all because they were all probably over-torqued at one time, stretched, and not providing the clamping force needed and at great risk of failing during operation. If it was just a weak bolt due to a void or large inclusion (very rare), you might take a chance and replace just that one.

jakec · « **Reply #11 on:** March 12, 2020, 05:00:57 PM »

it just twisted in two as I kept spinning it waiting for it to torque.

bryanj · « **Reply #12 on:** March 12, 2020, 05:44:32 PM »

Thats been overstressed, replace all 8 with nuts . Its cheaper than a new engine!!!

Don R · « **Reply #13 on:** March 12, 2020, 06:15:00 PM »

On many stock rebuilds we get away with re-using rod bolts but with any performance application replacing them is standard procedure. They list a maximum number of torque sequences but also recommend torqueing and loosening a couple times to ensure the bolt and nut get to know each other and you're getting a proper torque value.
Double check that wrench unless it's a known good calibration too.

jakec · « **Reply #14 on:** March 12, 2020, 09:59:16 PM »

the nuts are special, they have a asymmetrical side. I will see what they cost as well. already resigned to buy all 8 bolts. thanks guys

PeWe · « **Reply #15 on:** March 13, 2020, 01:22:48 AM »

You can find pictures with consequences of broken rod bolts if searching.
Not cheap nor safe.

jakec · « **Reply #16 on:** March 13, 2020, 09:17:58 AM »

The nuts are $10.26 each. LOL!

PeWe · « **Reply #17 on:** March 13, 2020, 11:19:29 AM »

That sounds expensive.
CB750 nut cost 3.5 Euro at CMSNL + VAT. If shipped outside EU, no VAT.

CB400F rod bolt nuts are expensive!!
https://www.cmsnl.com/honda-cb400f-general-export-mph_model14638/partslist/E01.html#.XmvPMLdwGKo

It can cost a lot more if not replacing them. If one broke by ease, all other probably bad.

I overtightened one HD cyl stud so it snapped. I replaced all since I had used a bad torque wrench tightening around 36Nm instead of 28Nm (20.65 ft lbs).

jakec · « **Reply #18 on:** March 13, 2020, 11:24:00 AM »

I think I'm going to get 8 bolts and just one nut. Total over $100!

PeWe · « **Reply #19 on:** March 13, 2020, 12:33:17 PM »

There is no good crank with rods on eBay for sale?
I do not know CB400, a good CB750 crank with rods on can be found for around 100USD.

Low shipping within USA, to Europe 80-100 more for shipping.

Like this
https://www.ebay.com/itm/151525085947

There are rods with bolts too.
Probably not tightened too hard.
https://www.ebay.com/itm/110869542656

jakec · « **Reply #20 on:** March 13, 2020, 12:58:54 PM »

I have a spare engine with a crank and rods inside it, but I thought the point was to get all new? At any rate, I went ahead and ordered all new ones from DSS earlier this morning.

BenelliSEI · « **Reply #21 on:** March 13, 2020, 07:29:05 PM »

Jake..... smart choice. Painful, but smart.

News:

Author Topic: Con Rod Clearance & One Broke (Read 1294 times)